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package java.awt.im;

import java.awt.Rectangle;
import java.awt.font.TextHitInfo;
import java.text.AttributedCharacterIterator;
import java.text.AttributedCharacterIterator.Attribute;

/**
 * InputMethodRequests defines the requests that a text editing component
 * has to handle in order to work with input methods. The component
 * can implement this interface itself or use a separate object that
 * implements it. The object implementing this interface must be returned
 * from the component's getInputMethodRequests method.
 *
 * <p>
 * The text editing component also has to provide an input method event
 * listener.
 *
 * <p>
 * The interface is designed to support one of two input user interfaces:
 * <ul>
 * <li><em>on-the-spot</em> input, where the composed text is displayed as part
 * of the text component's text body.
 * <li><em>below-the-spot</em> input, where the composed text is displayed in
 * a separate composition window just below the insertion point where
 * the text will be inserted when it is committed. Note that, if text is
 * selected within the component's text body, this text will be replaced by
 * the committed text upon commitment; therefore it is not considered part
 * of the context that the text is input into.
 * </ul>
 *
 * @author JavaSoft Asia/Pacific
 * @see java.awt.Component#getInputMethodRequests
 * @see java.awt.event.InputMethodListener
 * @since 1.2
 */

public interface InputMethodRequests {

  /**
   * Gets the location of a specified offset in the current composed text,
   * or of the selection in committed text.
   * This information is, for example, used to position the candidate window
   * near the composed text, or a composition window near the location
   * where committed text will be inserted.
   *
   * <p>
   * If the component has composed text (because the most recent
   * InputMethodEvent sent to it contained composed text), then the offset is
   * relative to the composed text - offset 0 indicates the first character
   * in the composed text. The location returned should be for this character.
   *
   * <p>
   * If the component doesn't have composed text, the offset should be ignored,
   * and the location returned should reflect the beginning (in line
   * direction) of the highlight in the last line containing selected text.
   * For example, for horizontal left-to-right text (such as English), the
   * location to the left of the left-most character on the last line
   * containing selected text is returned. For vertical top-to-bottom text,
   * with lines proceeding from right to left, the location to the top of the
   * left-most line containing selected text is returned.
   *
   * <p>
   * The location is represented as a 0-thickness caret, that is, it has 0
   * width if the text is drawn horizontally, and 0 height if the text is
   * drawn vertically. Other text orientations need to be mapped to
   * horizontal or vertical orientation. The rectangle uses absolute screen
   * coordinates.
   *
   * @param offset the offset within the composed text, if there is composed text; null otherwise
   * @return a rectangle representing the screen location of the offset
   */
  Rectangle getTextLocation(TextHitInfo offset);

  /**
   * Gets the offset within the composed text for the specified absolute x
   * and y coordinates on the screen. This information is used, for example
   * to handle mouse clicks and the mouse cursor. The offset is relative to
   * the composed text, so offset 0 indicates the beginning of the composed
   * text.
   *
   * <p>
   * Return null if the location is outside the area occupied by the composed
   * text.
   *
   * @param x the absolute x coordinate on screen
   * @param y the absolute y coordinate on screen
   * @return a text hit info describing the offset in the composed text.
   */
  TextHitInfo getLocationOffset(int x, int y);

  /**
   * Gets the offset of the insert position in the committed text contained
   * in the text editing component. This is the offset at which characters
   * entered through an input method are inserted. This information is used
   * by an input method, for example, to examine the text surrounding the
   * insert position.
   *
   * @return the offset of the insert position
   */
  int getInsertPositionOffset();

  /**
   * Gets an iterator providing access to the entire text and attributes
   * contained in the text editing component except for uncommitted
   * text. Uncommitted (composed) text should be ignored for index
   * calculations and should not be made accessible through the iterator.
   *
   * <p>
   * The input method may provide a list of attributes that it is
   * interested in. In that case, information about other attributes that
   * the implementor may have need not be made accessible through the
   * iterator. If the list is null, all available attribute information
   * should be made accessible.
   *
   * @param beginIndex the index of the first character
   * @param endIndex the index of the character following the last character
   * @param attributes a list of attributes that the input method is interested in
   * @return an iterator providing access to the text and its attributes
   */
  AttributedCharacterIterator getCommittedText(int beginIndex, int endIndex,
      Attribute[] attributes);

  /**
   * Gets the length of the entire text contained in the text
   * editing component except for uncommitted (composed) text.
   *
   * @return the length of the text except for uncommitted text
   */
  int getCommittedTextLength();

  /**
   * Gets the latest committed text from the text editing component and
   * removes it from the component's text body.
   * This is used for the "Undo Commit" feature in some input methods, where
   * the committed text reverts to its previous composed state. The composed
   * text will be sent to the component using an InputMethodEvent.
   *
   * <p>
   * Generally, this feature should only be supported immediately after the
   * text was committed, not after the user performed other operations on the
   * text. When the feature is not supported, return null.
   *
   * <p>
   * The input method may provide a list of attributes that it is
   * interested in. In that case, information about other attributes that
   * the implementor may have need not be made accessible through the
   * iterator. If the list is null, all available attribute information
   * should be made accessible.
   *
   * @param attributes a list of attributes that the input method is interested in
   * @return the latest committed text, or null when the "Undo Commit" feature is not supported
   */
  AttributedCharacterIterator cancelLatestCommittedText(Attribute[] attributes);

  /**
   * Gets the currently selected text from the text editing component.
   * This may be used for a variety of purposes.
   * One of them is the "Reconvert" feature in some input methods.
   * In this case, the input method will typically send an input method event
   * to replace the selected text with composed text. Depending on the input
   * method's capabilities, this may be the original composed text for the
   * selected text, the latest composed text entered anywhere in the text, or
   * a version of the text that's converted back from the selected text.
   *
   * <p>
   * The input method may provide a list of attributes that it is
   * interested in. In that case, information about other attributes that
   * the implementor may have need not be made accessible through the
   * iterator. If the list is null, all available attribute information
   * should be made accessible.
   *
   * @param attributes a list of attributes that the input method is interested in
   * @return the currently selected text
   */
  AttributedCharacterIterator getSelectedText(Attribute[] attributes);
}
